This invention pertains to imaging systems that employ opto-mechanical scanning reflectors for scanning an object and information processing circuitry for displaying an image of the object on a conventional television monitor. More specifically, the invention concerns a scan converter circuit for processing picture element information derived from sinusoidally oscillating reflectors so as to display on the television monitor an undistorted image of an object.
Imaging systems are used for producing an image representation of an object. To produce the image, the object is generally scanned by an opto-mechanical scanner. The scanner directs radiant energy from the object to a radiant energy sensor. A focusing lens also is usually placed in the optical path between the object and the sensor. The image is displayed on a display device, such as a CRT monitor. The radiance information obtained at the sensor is processed by an electrical circuit in a fashion so that it is compatible with the display circuitry of a display device. Scanners of this type are well known.
Difficulty often arises during assembly of the radiance information obtained from the sensor for producing an image that precisely depicts the object. For precisely depicting an image of the object, efforts have previously been directed to choosing a scanning mechanism that renders information that can conveniently be displayed with miminal signal processing or to choosing a display device that can conveniently be adapted to the signals produced by the scanning mechanism with minimal signal processing circuitry. However, a preferred scanning technique, such as sinusoidal raster scanning, is not always compatible with a preferred display device, such as a conventional television monitor. When using the preferred scanning mechanism and display device, the effort is directed to the most efficient and economical scan conversion network.
An efficient scan converter system is described in commonly assigned U.S. Pat. No. 3,978,281. It includes circuitry for converting picture information obtained during bi-directional raster scanning of an object scene to picture information that can be displayed on a linear scan CRT display monitor. The circuit includes means for reversing the order of sampled picture elements obtained during at least one half of the sweep cycle of an oscillating reflector. It also includes electronic circuitry for varying the sample rate of picture information in the object scene so that the picture elements can be displayed in real time by a conventional linear scanned television monitor.
A system directed to the problem of controlling the display rate of previously stored picture elements by a sinusoidally oscillating reflector is described in U.S. Pat. No. 4,037,231. This system projects onto a rotating drum medium stored picture elements during the linear portion (43%) of the position of a horizontal scan reflector. The picture elements are obtained from a buffer which receives its data from a memory device. During the remaining non-linear scan portion of the reflector, the buffer is again loaded with data from the memory device.
One objective of this invention though is to utilize as much of the horizontal scan portion of a sinusoidally oscillating reflector as possible without image distortion and thereby improve the overall scanning efficiency of image forming scanning systems.
Another objective of the invention is to improve the image quality in scanning systems using raster scanning mechanisms for scanning an object and a CRT display device for displaying an image of the object.
Another objective of the invention is to provide a common high "Q" synchronizing apparatus for timing the operation of the sampling and display control circuits.
Other objectives will become more readily apparent upon review of the succeeding disclosure.